Machine tool

ABSTRACT

An improved machine tool for operating on bar stock includes a gripper which is moved away from a chuck to pull bar stock to a work station. When the gripper has been moved through a distance sufficient to pull a desired length of bar stock to the work station, a numerical control system is effective to interrupt movement of the gripper and bar stock. The numerical control system enables different lengths of bar stock to be fed to the work station on successive cycles of operation of the machine tool in response to stored numerical control data. In one embodiment of the machine tool, the gripper is advantageously mounted on a turret which supports tools and is operated by the numerical control system in accordance with a predetermined program to machine the length of bar stock fed to the work station.

United States Patent Blake 51 Aug. 19, 1972 1 MACHINE TOOL [72]Inventor: Charles T. Blake, Shaker Heights,

Ohio

[73] Assignee: The Warner 8: Swasey Company,

Cleveland, Ohio [22] Filed: June 11, 1970 [21] Appl. No.: 45,478

[52] U.S. Cl. ..82/2.5, 82/2 B, 2l4/l.l [51] Int. Cl. ..B23b 15/00 [58]Field of Search ..82/2.5, 2 B, 2.7; 2l4/1.l; 29/27 [56] References CitedUNITED STATES PATENTS 3,486,209 12/1969 Shultz et al ..29/27 3,324,3646/1967 Caruthers ..82/2 B 3,200,680 8/l965 Coffin ..82/2.5 3,131,5875/1964 Spohn et al ..82/2.7 3,101,019 8/1963 LeLan ..82/2.5 489,935l/l893 Conradson ..2l4/l.1

932,394 8/1909 Johnson ..2l4/l.l

Primary Examiner-Leonidas Vlachos Attorney-Yount and Tarolli 57 ABSTRACTAn improved machine tool for operating on bar stock includes a gripperwhich is moved away from a chuck to pull bar stock to a work station.When the gripper has been moved through a distance sufficient to pull adesired length of bar stock to the work station, a numerical controlsystem is effective to interrupt movement of the gripper and bar stock.The numerical control system enables different lengths of bar stock tobe fed to the work station on successive cycles of operation of themachine tool in response to stored numerical control data. In oneembodiment of the machine tool, the gripper is advantageously mounted ona turret which supports tools and is operated by the numerical controlsystem in accordance with a predetermined program to machine the lengthof bar stock fed to the work station.

12 Claims, 5 Drawing Figures Illllllllli mmcosmem 3.691.879

sum 1 or 4 //VVE/V7'0/? CHARLES 7: 8LAK ATTORNEYS PAIENTEBSEP 19 m2SHEET 3 OF 4 MQE smkmxm QQRQSQU MACHINE TOOL This invention relates to anew and improved method and apparatus for feeding bar stock to a workstation in a machine.

Commercial machine tools for operating on bar stock commonly includeexternal bar stock feed assemblies. During each cycle of operation ofone of these machine tools, the associated feed assembly is operated topush a predetermined length of bar stock to a work station at which itis operated on by the machine tool. If

the length of bar stock fed to the work station is to be changed fromone cycle of the machine tool to the next, operation of the machine toolmust be interrupted between the successive cycles to adjust the feedassembly to feed the desired length of bar stock on the next cycle ofthe machine tool. Of course, interrupting operation of the machine toolto adjust the feed assembly reduces the overall operating efficiency ofthe machine tool.

Accordingly, it is an object of this invention to provide a new andimproved machine tool having an internal bar stock feed assembly whichis operable to feed bar stock without providing an external bar stockfeed assembly.

Another object of this invention is to provide a new and improvedmachine tool having a bar stock feed assembly which is automaticallyoperable to feed different, predetermined lengths of bar stock to a workstation on successive cycles of operation of the machine tool.

Another object of this invention is to provide a new and improvedmachine for operating on bar stock and which includes a gripper forengaging the bar stock and pulling it in a direction away from a chuckto thereby feed a length of the bar stock to a work station.

Another object of this invention is to provide a new and improvedmachine in accordance withv the next preceding object and including aturret for supporting tools for operating on the length of bar stock atthe work station and wherein the gripper is mounted on the turret formovement therewith relative to the chuck.

Another object of this invention is to provide a new and provedmachinehaving numerical control means for effecting movement of a gripper andbar stock gripped thereby to feed a predetermined length of bar stock toa work station, the numerical control means being responsive to storednumerical data to interrupt movement of the gripper and bar stock whenthey have moved through a distance in accordance with the storednumerical data.

Another object of this invention is to provide a new and improvedmachine in accordance with the next preceding object and wherein thenumerical control means is responsive to a predetermined program and isoperable to interrupt movement of the gripper at different locationsrelative to a base of the machine on successive cycles of operation ofthe machine to thereby enable the length of bar stock fed to the workstation to be varied on successive cycles of operation in accordancewith the predetermined program.

Another object of this invention is to provide a new and improved methodof operating a machine for working on bar stock with tools located in awork area wherein the method includes the steps of holding the bar stockin a chuck, gripping the bar stock with a gripper, and pulling bar stockfrom the chuck to the work area by moving the gripper and the bar stockgripped thereby in a direction away from one end portion of the chuck.

Another object of this invention is to provide a new and improved methodof operating a machine for work on bar stock with tools located in awork area wherein the method includes the steps of gripping the barstock while it is being held by a chuck, moving the gripper assembly andbar stock gripped thereby relative to the chuck to thereby feed aportion of the bar stock to the work area, generating signals fordetermining the position of the gripper assembly as the bar stock andthe gripper assembly are being moved to feed bar stock, and stoppingmovement of the gripper assembly and bar stock when the signals indicatethat the gripper assembly has been moved through a distance to feed adesired length of bar stock to the work area.

These and other object and features of the invention will become moreapparent upon consideration of the following description taken inconnection with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a machine tool constructed inaccordance with the present invention;

FIG. 2 is an enlarged, fragmentary sectional view of a spindle assemblyof the machine tool of FIG. I;

FIG. 3 is a schematic illustration depicting the relationship betweenthe spindle assembly, a turret on which a gripper for engaging bar stockheld by the spindle assembly is mounted, and a numerical control systemfor controlling movement of the turret and gripper to feed apredetermined length of the bar stock to a work station;

FIG. 4 is a fragmentary schematic illustration depicting the engagementof the gripper with a leading end portion of the bar stock; and

FIG. 5 is a schematic illustration of a numerical control system forcontrolling the feeding of bar stock to the work station.

A machine tool 10 having a bar stock feeding apparatus constructed inaccordance with the present invention is illustrated in FIG. 1. Themachine tool 10 is a well known saddle-type turret lathe and includes aheadstock 12 in which a spindle assembly 14 (see FIGS. 1 and 2) ismounted. Although the machine tool 10 is a turret lathe having only asingle spindle assembly 14, it is contemplated that bar feed apparatusconstructed in accordance with the present invention could be used inmultiple spindle machines and in machines other than turret lathes.

The spindle assembly 14 includes a collet chuck 16 having jaws 18 (FIG.2) for gripping bar stock 20 and holding the bar stock against axialmovement while the bar stock is being rotated by the spindle assembly14. An actuator assembly 22 operates the jaws 18 of the chuck 16 betweena closed condition (FIG. 2) in which the jaws securely grip the barstock 20 and an open condition in which the bar stock is released foraxial movement relative to the spindle assembly 14. Although it iscontemplated that many different types of spindle assemblies can beutilized, in a specific preferred embodiment of the invention thespindle assembly I4 is the same as disclosed in U.S. Pat. No. 2,546,326to Wetzel. In order to avoid prolixity of description, the disclosuretherein is hereby incorporated into this specification by this referencethereto.

The spindle assembly 14 is operable to rotate the bar stock with aleading end portion 24 of the bar stock extending into a work ormachining station (FIG. 1) where it is machined in a known manner tools34 mounted on a turret 36. The turret 36 is rotatable about a centerpivot 40 to index the various tools 34 to working positions relative tothe leading end portion 24 of bar stock 20. The turret 36 is mounted ona crossslide 42 (FIG. 3) for' crosswise movement to position a selectedtool 34 transversely relative to the bar stock 20. This transversemovement of the carriage 42 is guided by ways or tracks 44 which extendperpendicular to longitudinal axesof the bar stock 20 and spindleassembly 14. The ways 44 are mounted on a saddle or carriage 48 which ismovable along tracks or ways 50 in a work area 52 which extends awayfrom the headstock 12 for substantially the entire length of a base 53(FIG. 1) of the machine tool 10. By moving the saddle 48 along the ways50 which are parallel to the longitudinal axis of the spindle assembly14, the position of the tools 34 can be adjusted longitudinally alongthe end portion 24 of the bar stock 20 and the base 53 of the machinetool 10.

At the end of a cycle of operation of the machine tool 10, the leadingend portion of the bar stock 20 is severed from the remainder of the barstock by operation of a cut-off tool 54 (see FIG. 3). For purposes ofclarity of illustration, the cutoff tool 54 has been omitted fromFIG. 1. Operation of the cutoff tool 54 leaves a relatively shortportion of the bar stock 20 extending from the chuck 16 into the workarea 52, as shown in solid lines in FIG. 3.

When the next piece or part is to be machined from the bar stock 20, theleading end portion 24 of the bar stock must be fed to the work ormachining station 30. To accomplish this, the relatively short leadingend portion 24 of the bar stock is clampingly engaged by a gripper 56.The chuck 16 is then opened and a desired length of the bar stock 20 ispulled to the work station 30 by moving the gripper 56 away from thechuck 16, that is toward the right as viewed in FIG. 3. When the desiredlength of bar stock 20 has been pulled to the work station 30, thepulling movement of the gripper 56 is interrupted and the chuck 16 isoperated to the closed condition to hold the bar stock against furtheraxial movement. The gripper 56 is then disengaged from the bar stockwhich is machined by suitable operation of the machine tool 10.

The gripper 56 is brought into gripping engagement with the bar stock 20by pressing the gripper axially onto the leading end portion 24 of thebar stock, in the manner illustrated in FIG. 4. Clampingor grippingsurfaces 60 on the interior of resilient finger elements 62 clampinglyengage the leading end portion 24 of the bar stock 20 to grip the barstock. To provide for this clamping engagement, the surfaces 60 (FIG. 4)on the 'interior of the finger elements 62 define an opening having acrosssectional configuration which is similar to and slightly smallerthan the cross-sectional configuration of the bar stock 20. Therefore,the resilient fingers 62 are cammed slightly outwardly by the pressingengagement of sloping or beveled ends 64 of the resilient fingers withthe leading end portion 24 of the bar stock 20 as the gripper 56 ispressed axially toward the spindle assembly 14. To minimize anypossibility of damaging the chuck 16, the axial motion of the gripper 56toward the chuck 16 is stopped with vthe ,open end portion of thegripper spaced a predetermined distance from the leading side of thechuck.

After the leading end portion 24 of the bar stock 20 has been clampinglyengaged by the gripper 56, the chuck 16 is operated to the opencondition to release the bar stock. The gripper 56 is then moved apredetermined distance away from the spindle assembly 14 to pull adesiredlength of the bar stock 20 to the machining position 30 (FIG. 3).To prevent the bar stock 20 from being bent or deflected relative to thespindle assembly 14, the gripper 56 is moved along a straight path whichis coincident with the longitudinal axes of the bar stock 20 and spindleassembly 14 as the bar stock is pulled from the leading or work side ofthe chuck 16.

After the gripper 56 has been moved through a predetermined distanceaway from the spindle assembly 14 to pull a predetermined length of thebar stock 20 into the machining position 30, the movement of the gripper56 is stopped. The chuck 16 is then operated to the closed condition toretain the predetermined length of bar stock 20 at the work or machiningstation 30. After this has been accomplished, the gripper 56 isdisengaged from the leading end portion 24 of the bar stock 20 bycontinuing the movement of the gripper away from the now closed chuck16. As the movement of the gripper 56 away from the closed chuck 16 iscontinued, the clamping or friction surfaces 60 of the resilient fingers62 (FIG. 4) slide along a longitudinally extending outer surface of thebar stock 20 and off of the leading end of the bar stock while the barstock is held against axial movement relative to the chuck.

The gripper 56 is advantageously mounted on the turret 36 so that adrive assembly (FIG. 3) for moving the saddle 48 along the bed ways 50and a drive assembly 72 for moving the cross-slide 42 along the ways ortracks 44 can be utilized to accurately position and move both the tools34 and the gripper 56 relative to the spindle assembly 14. In addition,mounting the gripper 56 on the turret 36 enables common numericalcontrol circuitry 76 to be utilized to control movement of the gripper56 (FIG. 1) relative to the spindle assembly l4 and to control movementof the tools 34 in machining the bar stock 20. However, it iscontemplated that in certain machines it may be desirable to provide oneassembly for moving the gripper 56 and another assembly for movingtools, similar to the tools 34, relative to bar stock at a work station.

The numerical control circuitry 76 is operable to effect movement of theturret 36 and gripper 56 to pull a predetermined length of the bar stock20 to the work station 30 and to effect movement of the tools 34 tooperate on this predetennined-length of bar stock. The control circuitry76 operates the machine tool 10 through a plurality of cycles ofoperation in accordance with a predetermined program which is recordedon a punched tape 80. In the specific embodiment of the controlcircuitry 76 illustrated in FIG. 3, the tape 80 is stepped or indexed bya reader 82 in response to either the completion of a predetermined stepin an operating cycle or in response to an indication on the tape.However, it is contemplated that buffer storage could be used to enablethe tape to be read at least one step in advance and that the controlcircuitry could be constructed in accordance with US. Pat. No. 3,431,478issued to J. N. Forrester et al. or US. Pat. No. 3,190,139 issued to E.S. Swanson et al. It is also contemplated that either an absolute orincremental type control system could be used if desired.

At the beginning of a cycle of operation of the machine tool 10, theturret 36 is operated to position the gripper 56 in axial alignment withthe bar stock 20. To accomplish this, the turret 36 is indexed inaccordance with data read from the tape 80 and sent over a path orconnection 84 to a numerical control system 86. In response to thiscommand data, the numerical control system 86 sends a control signalover a path or connection 90 to a drive mechanism 92 on the crossslide42. The drive mechanism 92 then rotates or indexes the turret 36 to theposition illustrated in FIG. 3 in which the open end of of the gripper56 faces toward the spindle assembly 14. A feedback signal is sent alonga path or connection 94 to the numerical control system 86 to indicatethe completion of this indexing operation. Upon receipt of this feedbacksignal, the numerical control system 86 transmits a signal on a lead 96to the reader 82 which steps the tape 80. The reader 82 thereupon readsthe tape 80 and relays numerical data stored on the tape to thenumerical control system 86. This numerical data represents a numericalcorresponding to the displacement of the turret 36 from a referenceposition on the saddle 48 when a longitudinal axis of the gripper 56 isaligned with the longitudinal axis of the bar stock 20.

Upon receipt of this data, the numerical control system 86 sends acontrol signal on a lead 100 to operate a servomotor 102 in thecross-slide drive assembly 42. The servomotor 102 is operated in theproper direction to rotate a drive screw 104 and thereby more thecross-slide 42 to a position (FIG. 3) in which the gripper 56 is axiallyaligned with the spindle assembly 14. During this movement of thecrossslide 42, an encoder or a signal generator 108 transmits electricalsignals indicative of the existing displacement of the turret 36 andgripper 56 from a reference or zero position on the saddle 48. When thisfeedback signal corresponds to the numerical data stored in the controlsystem 86, the control system interrupts operation of the servomotor 102and transmits a signal to the reader 82 to step the tape 80.

Once the gripper 56 has been aligned with the bar stock 20, the gripperis moved toward the chuck l6 and into engagement with the relativelyshort end portion 24 of the bar stock 20. Accordingly, the reader 82reads the tape 80 and transmits command data representing a referencenumber which is determinative of the displacement of the saddle 48 andturret 36 relative to a zero or reference position when the gripper 56grips the end portion 24 of the bar stock (FIG. 4). In response to thiscommand data, the numerical control system 86 transmits a control signalalong a path or connection 114 to a servomotor 116 which rotates a drivescrew 118 to move the saddle 48 along the bed ways 50 toward the chuck16. As the saddle 48 and gripper 56 are moved toward the chuck 16 bythis operation of this drive assembly 70, feedback signals aretransmitted from an encoder or signal generator 122 through a path orconnection 124 to the numerical control system 86. These feedbacksignals represent numbers which are indicative of the instantaneous orexisting displacement of the saddle 48 and turret 36 from a zero orreference position relative to the spindle assembly 14. When the gripper56 has been pressed onto the leading end portion 24 of the bar stock 20(FIG. 4), the feedback signal from the encoder 122 corresponds to thereference or command data in the numerical control system 86. Thenumerical control system 86 thereupon interrupts operation of theservomotor 116 to stop the movement of gripper 56 toward the chuck 16and simultaneously therewith transmits a signal to the tape reader 82 toindex the tape 80.

After the gripper 56 has engaged the leading end of the bar stock 20,the chuck 16 is operated to the open condition and the gripper 56 ismoved away from the spindle assembly 14 to pull a predetermined lengthof the bar stock to the work or machining position 30. Therefore, thenext step on the tape 80 activates the reader 82 to send a commandsignal to the numerical control system 86 which in turn transmitssignals along a path or connection 130 to the chuck actuator 22 toeffect operation of the chuck 16 to the open condition. After a timedelay sufficient to enable the chuck 16 to open, the tape 80 is againstepped and numerical data stored thereon and determinative of thelength of bar stock to be pulled to the machining position 30 is readand transmitted to the numerical control system 86.

Upon receipt of this data, the numerical control system 86 againactivates the servomotor 116 to operate the drive assembly 70. However,this time the direction of operation of the drive assembly is reversedto move the saddle 48 and the turret 36 away from the spindly assembly14 so that the gripper 56 pulls the leading end portion of the bar stock20 to the machining position 30. As the gripper 56 pulls the bar stockto the machining position 30, the encoder 122 transmits feedbacksignals. These feedback signals are determinative of the change inlocation of the turret 36 and gripper 56 relative to a referenceposition and, therefore, of the length of bar stock which has beenpulled to the machining position 30. When the predetermined length ofbar stock has been pulled to the machining position 30, that is when afeedback signal from the encoder 122 corresponds to the numerical datastored in the numerical control system 86, the numerical control systeminterrupts operation of the servomotor 116 and transmits a signal to thereader 82 to effect a stepping of the tape 80. In the specific preferredembodiment of the invention illustrated herein, the feedback signalsfrom the encoder 122 are uniquely representative of the position of thegripper 56 relative to the base 53. However, it is contemplated that apulse type feedback signal generator could be used and the pulsescounted to determine the position of the gripper.

Once the desired length of bar stock 20 has been pulled to the machiningposition 30, the chuck 16 is operated to the closed condition to holdthe bar stock against further axial movement and the gripper 56 isdisengaged from the bar stock by continuing the movement of the gripperaway from the spindle assembly. Accordingly, a suitable indication onthe tape activates the reader 82 to send a command signal to thenumerical controlsystem 86. Upon receipt of this command signal, thenumerical control system 86 sends a control signal over the path 130 tothe chuck actuator 22 to effect operation of the chuck 16 to the closedcondition. After the chuck has been closed, the tape 80 is again steppedand command signals representing numerical data determinative of aposition of the saddle 48 in which the open end of the gripper 56 isspaced from the leading end of the bar stock 24, are transmitted to thenumerical control system 86. Upon receipt of this command data, thenumerical control system 86'activates the servomotor 1 16 to continuethe movement of the turret 36 in a direction away from the spindleassembly 14. Since the chuck 16 is in the closed condition, the barstock is held against axial movement and the resilient fingers 62 of thegripper 56 slide along the outer surface of the bar stock 20 until thegripper 56 is disengaged from the bar stock. When the gripper 56 isspaced a desired distance from the end of bar stock, a feedback signalfrom the encoder 122 corresponds to the command or reference data storedin the numerical control system 86 and the servomotor l 16 isde-energized.

A drive assembly 134 is then activated to rotate the spindle assembly14, which is supported by bearings 136, to rotate the bar stock 20 aboutits longitudinal axis. The turret 36 is then indexed, in accordance withthe data stored on the tape 80, to move any one of the tools 34 to anoperating position relative to the leading end portion of the bar stock20. The saddle and crossslide drive assemblies 70 and 72 are alsooperated in accordance with data recorded on the tape 80 to move thetools 34 into engagement with the length of bar stock at the machiningposition 30. From time to time during operation of the machine tool 10,the turret 36 will be indexed to bring other tools into the workingposition and the turret will be moved axially and transversely relativeto the bar stock to perform machining operations dictated by the programstored on the tape 80.

.Toward the end of the cycle of operation of the machine tool 10, thecut-off tool 54 is moved into engagement with the rotating bar stock 20to sever the machined piece of bar stock from the main portion of thebar stock. Accordingly, the tape 81 activates the reader 82 to transfera command signal to the numerical control system 86 which transmits acontrol signal over a path or connection 142 to a drive mechanism 144for the cut-off tool 54. Activation of the drive mechanism 144 moves thecut-off tool 54 into engagement with the bar stock 20 to sever themachined end portion from the bar stock. Upon completion of this cuttingor severing, the cut-off tool 54 is retracted and afeedback signal istransmitted over a path or connection 150 to the numerical controlsystem 86. In response to this feedback signal, the numerical controlsystem 86 again activates the reader 82 to step the tape 80 to begin thenext succeeding cycle of the machine tool 10.

The machine tool 10 is capable of machining parts having different axiallengths on different cycles of operation of the machine tool. This canbe accomplished without interrupting the operation of the machine tool10 by merely storing on the tape 80 suitable data which corresponds tothe lengths of bar stock 20 to be fed to the work station 30 on thesuccessive cycles of operation of the machine tool. Thus on one cycle ofoperation of the machine tool 10, the data recorded on the tape can besuch that the servomotor 116 would be de-energized to interrupt pullingmovement of the bar stock 20 toward the work station 30 after thegripper 56 has been moved for a relatively small distance from the chuck16. On the next succeeding cycle of operation of the machine tool 10,the data stored on the tape 80 could be such as to cause the operationof the servomotor 116 to be interrupted after the gripper 56 has movedaway from the chuck 16 by a relatively large distance. Therefore, apiece or part having a relatively short axial extent would be machinedon the first of the foregoing operating cycles while a piece or parthaving a relatively long axial extent would be machined on the second ofthe foregoing operating cy-.

cles of the machine tool 10. It should be noted that this change ofaxial lengths of the parts machined on successive operations of themachine tool 10 is obtained without shutting down or interrupting theoperation of the machine tool to adjust a bar feed mechanism.

In the embodiment of the control circuitry 76 disclosed in FIG. 3, thetape 80 is stepped or indexed on completion of each successive step of abar stock feeding operation. Numerical control circuitry which enablesthe bar stock feeding operation to be accomplished without indexing thetape 80 upon the completion of each step of the operation is illustratedsche- 'matically in FIG. 5. The numerical control circuitry 170 of FIG.5 is associated with suitable control circuitry to align the gripper 56with the chuck 16 by indexing the turret 36 and operating the servomotor102 and to operate the spindle drive 134 and cut-off drive 144. Sincethe operation of the associated circuits will be understood from theforegoing description of the numerical control circuitry 76, theseassociated circuits have been omitted in FIG. 5 for purposes of clarityof illustration and to avoid unnecessary prolixity of description.

The numerical control circuitry 170 includes a plurality of registers172, 174 and 176 for storing numerical data which is determinative ofthe positions to which the gripper 56 is to be moved by operation of theservomotor 16 during a bar stock feeding operation. This data istransmitted from each of the registers 172, 174 and 176 in turn to aerror detector 178 in a servo system 180. The error detector 178 iseffective to transmit an error or control signal to an amplifier 18]which operates the servomotor 116 in a proper direction to move thesaddle 48 and gripper 56 to a position corresponding to the datatransmitted to the error detector 178. The sequence in which thenumerical data is transmitted from the registers 172, 174 and 176 to theerror detector 178 where it is temporarily stored is controlled by acounter 182. The counter 182 steps between four positions, i.e., zero tothree, and is returned to the zero position at the end of a cycle.

At the start of a bar stock feeding operation, the tape 80 is read bythe reader 82 which transmits recorded numerical data corresponding tothe position in which the gripper 56 engages the leading end portion ofthe bar stock 24 (FIG. 4), over path 186 (FIG. 5) to the register 172where the numerical data is stored. Numerical data recorded on the tape80 and corresponding to the position of the gripper 56 when the desiredlength of the bar stock has been fed to the work station 30 istransmitted from the reader 82 over path 188 to the register 174 whereit is stored. Similarly, numerical data corresponding to the position towhich the gripper 56 has to be moved to disengage the gripper from theleading end of the bar stock once the desired length of the bar stockhas been pulled to the work station is transmitted from the tape reader82 over path 190 to the register 176 where this data is stored. It iscontemplated that in certain machine tools the registers 172, 174 and176 may be manually adjusted to store the desired numerical data.

After the numerical data indicating the various positions of movement ofthe gripper has been read from the tape 80, the tape reader 82 sends asignal over a lead 194 to actuate a start bar feed flip-flop 196. Theflip-flop 196 thereupon transmits a signal to and AND gate 200 which isnow conditioned by the zero output of the counter 82. The output fromthe AND gate activates suitable AND gating circuitry 208 to enable thenumerical data stored in the register 172 to be transmitted to the errordetector 178 where the numerical data is temporarily stored.

On receipt of the numerical data from the register 172, the errordetector 178 compares the actual position of the saddle 48 with acommanded position represented by the numerical data from the register.An error signal is then transmitted to the amplifier 181 which operatesthe servomotor 116 in a direction determined by the polarity of theerror signal and at a rate dependent upon the magnitude of the errorsignal. This operation of the servomotor 116 moves the gripper 56 intoengagement with the leading end portion 24 of the bar stock 20. Thus,the servomotor 1 16 is energized to rotate the drive screw 118 (FIG. 3)to move the saddle 48 and gripper 56 toward the chuck 16. When thegripper has engaged the leading end portion of the bar stock 20, theactual position of the saddle 48 will correspond to the command positionand the error signal from the error detector 178 will be zero. A nulldetector 214 detects when error signal changes to zero, that is when thegripper 56 has engaged the leading end portion 24 of the bar stock 20,and thereupon transmits a signal to the counter 182 to step the counterfrom the zero position to the first position.

After the leading end portion 24 of the bar stock 20 has been engaged bythe gripper 56, the chuck 16 must be operated to the open condition andthe gripper 56 moved away from the chuck to pull a desired length of barstock to the work station 30. Accordingly, stepping the counter 182 tothe first position sets a chuck actuator bistable flip-flop 218 to senda signal over a path 220 to the chuck actuator 22 to operate the chuck16 to the open condition. In addition, a signal is sent over a path 224to AND gating 226 whereupon the numerical data stored in the register174 is transmitted to the error detector 178 and the servomotor 116 isenergized to move the gripper away from the chuck 16. As the gripper 56is being moved away from the chuck 16, the encoder 122 transmits toerror detector 178 feedback signals determinative of the existing orinstantaneous position of the gripper relative to the chuck 16. When afeedback signal from the encoder 122 matches or corresponds to thenumerical data stored in the error detector 178, the error signalreaches zero and operation of the motor 116 is interrupted. Of coursewhen the error signal changes to zero, the null detector 214 sends asignal to the counter 182 to step the counter to the second position.

After the desired length of bar stock has been fed to the work station30 by the foregoing movement of the gripper 56 away from the chuck 16,the chuck is operated to the closed condition to hold the bar stock 20against further axial movement relative to the work station 30. Afterthe chuck 16 has been closed, the

gripper 56 is disengaged from the leading end portion 24 of the barstock 20 by continuing movement of the gripper 56 in the direction awayfrom the chuck 16. To accomplish this upon a stepping of the counter tothe second position, the chuck actuator flip-flop 218 is actuated totransmit a signal over a path 230 to the chuck actuator 22 whichthereupon actuates the chuck 16 to the closed condition.

After the chuck 16 has been closed, a signal is transmitted over a path232 to AND gating 234. The numerical data stored in the register 176 isthen transmitted to the error detector 178 which operates the servomotor116 to continue movement of the gripper 56 away from the chuck 16. Sincethe bar stock 20 is now held against axial movement by the closed chuck16, the continued movement of the gripper 56 pulls it off the leadingend portion 24 of the bar stock 20. After the gripper 56 has becomedisengaged from the bar stock 20, a feedback signal from the encoder 122matches the'data in the error detector 178 which then changes the errorsignal to zero to de-energize the servomotor 116 and cause the nulldetector 214 to send a signal to step the counter 182 to the thirdposition.

When the gripper 56 is disengaged from the bar stock 20, the machinetool 10 is ready to begin machining operations on the bar stock at thework station 30 in accordance with a program recorded on the tape 80.Therefore, stepping the counter 182 to the third position transmits asignal to the tape reader 82 over a path 238 to index the tape 80. Inaddition, a signal from the counter 182 actuates the start feedflip-flop 196 to interrupt the transmission of a signal to the AND gate200. The start bar feed flip-flop 196 has a re-set output which resetsthe counter 182 at the end of the bar feed cycle and holds the counterin a reset condition until the bar feed flip-flop 196 is again set tostart a new cycle.

From the foregoing description, it can be seen that the machine tool 10includes a gripper 56 which is moved away from the chuck 16 to feed thebar stock 20 by pulling it to the machining position 30. It should benoted that the provision of the gripper 56 eliminates the necessity ofproviding an external bar stock feed assembly as has heretofore been acommon practice during operation of commercial machine tools. Thegripper 56 is advantageously mounted on the turret 36 so that commondrive and control assemblies can be used to effect accurate movement ofthe gripper 56 to feed a predetermined length of bar stock to a workstation 30 and to position the tools 34 relative to this predeterminedlength of bar stock. The numerical control circuitry 76 is operated inaccordance with a predetermined program recorded on tape 80 to activatethe saddle drive assembly 70 to feed a predetermined length of bar stockto the machining position 30. This predetermined length of bar stock canbe varied from one cycle of the machine tool to the next by merelyrecording the proper program on the tape 80. Therefore, pieces ofdifferent lengths can be machined on different cycles of the machinetool without interrupting the operation of the machine tool to adjust anassociated bar stock feed assembly to feed a different length of barstock corresponding to the desired length of the next piece to bemachined.

Having described a specific preferred embodiment of the invention, thefollowing is claimed:

1. A machine for operating on bar stock with tools located in aworkarea, said machine comprising chuck means for holding bars stock ina'position in which the barstock extends away from one end portion ofsaid chuck means into the work area, said chuck means being operablebetween a closed condition holding the bar stock against movementrelative to said chuck means and an open condition in which the barstock is movable relative to said chuck means, actuator means foreffecting operation of said chuck means between the open condition andthe closed condition, gripper means for gripping the bar stock in thework area adjacent to said one end portion of said chuck means, saidgripper means including a plurality or resilient finger elements havingsurfaces defining an opening which is slightly smaller than and has thesame general crosssectional configuration as the cross-sectionalconfiguration of one end portion of the bar stock, means for moving saidgripper means away from said one end portion of said chuck means to pullbar stock from said chuck means into the work area by moving the portionof bar stock gripped by said gripper means away from said one endportion of said chuck means when said chuck means has been operated tothe open condition by said actuator means, said means for moving saidgripper means being operable to effect gripping engagement of saidgripper means with the bar stock by moving said gripper means towardsaid one end portion of said chuck means when said chuck means is in theclosed condition to press the finger elements against the one endportion of the bar stock and cam the finger elements outwardly toincrease the size of the opening slightly and to move the fingerelements into frictional engagement with an axially extending surface ofthe one end portion of the bar stock while the bar stock is held againstaxial movement by said chuck, means, and control means for controllingthe operation of said actuator means and said means for moving saidgripper means, said control means including means for effectingoperation of said actuator means to operate said chuck means to theclosed condition after bar stock has been pulled from said chuck meansby movement of said gripper means away from said one end portion of saidchuck means and means for disengaging said gripper means from the barstock by continuing the movement of said gripper means away from saidone end portion of said chuck means after said chuck means has beenoperated to the closed condition by said actuator means to slide saidfinger elements out of frictional engagement with the one end portion ofthe bar stock.

2. A machine for operating on bar stock with tools located in a workarea, said machine comprising chuck means for holding bar stock in aposition in which the bar stock extends away from one end portion ofsaid chuck means into the work area, said chuck means being operablebetween a closed condition holding the bar stock against movementrelative to said chuck means and an open condition in which the barstock is movable relative to said chuck means, actuator means foreffecting operation of said chuck means between the open condition andthe closed condition, gripper means for gripping the bar stock in thework area ad jacent to said one end portion of said chuck means, saidgripper means includes a plurality of resilient finger elements havingsurfaces defining an opening which is slightly smaller than and has thesame general crosssectional configuration as the cross-sectionalconfiguration of one end portion of the bar stock, means for moving saidgripper means away from said one end portion of said chuck means to pullbar stock from said chuck means into the work area by moving the portionof bar stock gripped by said gripper means away from said one endportion of said chuck means when said chuck means has been operated tothe open condition by said actuator means, said means for moving saidgripper means being operable to effect gripping engagement of saidgripper means with the bar stock by moving said gripper means towardsaid one end portion of said chuck means when said chuck means is in theclosed condition to press the finger elements against the one endportion of the bar stock and cam the finger elements outwardly toincrease the size of the opening slightly and to move the fingerelements into frictional engagement with an axially extending surface ofthe one end portion of the bar stock while the bar stock is held againstaxial movement by said chuck means, and numerical control means forcontrolling operation of said means for moving said gripper means tothereby control the length of bar stock pulled from said chuck means,said numerical control means including register means for storingnumerical data which is in accordance with the length of bar stock to bepulled from said chuck means by movement of said gripper means away fromsaid one end portion of said chuck means and control means forinterrupting operation of said means for moving said gripper means inresponse to the pulling from said chuck means of a length of bar stockwhich is in accordance with the numerical data stored in said registermeans.

3. A machine for operating on bar stock with tools located in a workarea, said machine comprising chuck means for holding bar stock in aposition in which the bar stock extends away from one end portion ofsaid chuck means into the work area, said chuck means being operablebetween a closed condition holding the bar stock against movementrelative to said chuck means and an open condition inwhich the bar stockis movable relative to said chuck means, actuator means for effectingoperation of said chuck means between the open condition and the closedcondition, gripper means for gripping the bar stock in the work areaadjacent to said one end portion of said chuck means, said gripper meansincluding surface means for frictionally engaging one end portion of thebar stock, means for moving said gripper means away from said one endportion of said chuck means to pull bar stock from said chuck means intothe work area by moving the portion of bar stock gripped by said grippermeans away from said one end portion of said chuck means when said chuckmeans has been operated to the open condition by said actuator means,said means for moving said gripper means being operable to effectgripping engagement of said gripper means with the bar stock by movingsaid gripper means toward said one end portion of said chuck means whensaid chuck means is in the closed condition to press said gripper meansagainst the one end portion of the bar stock and move said surface meansinto frictional engagement with an axially extending surface of the oneend portion of the bar stock while the bar stock is held against axialmovement by said chuck means, and control means for controlling theoperation of said actuator means and said means for moving said grippermeans, said control means including means for disengaging said grippermeans from the bar stock by continuing the movement of said grippermeans away from said chuck means after said chuck means has beenoperated to the closed condition by said actuator means and sliding saidsurface means along the one end portion of the bar stock to move saidsurface means out of frictional engagement with the one end portion ofthe bar stock.

4. A machine as set forth in claim 2 wherein said numerical controlmeans further includes means for operating said machine through aplurality of operating cycles in accordance with a predetermined programand means for enabling the stored numerical data to vary in accordancewith the predetermined program on successive cycles of operation of saidmachine to enable the predetermined length of bar stock pulled from saidchuck means into the work area to be varied on successive cycles ofoperation of said machine.

5. A machine as set forth in claim 1 wherein said control means includesnumerical control means for controlling operation of said means formoving said gripper means to thereby control the length of bar stockpulled from said chuck means, said numerical control means includingregister means for storing numerical data which is in accordance withthe length of bar stock to be pulled from said chuck means by movementof said gripper means away from said one end portion of said chuck meansand control means for interrupting operation of said means for movingsaid gripper means in response to the pulling from said chuck means of alength of bar stock which is in accordance with the numerical datastored in said register means.

6. A machine as set forth in claim 5 wherein said numerical controlmeans further includes means for operating said machine tool through aplurality of operating cycles in accordance with a predetermined programand means for enabling the stored numerical data to be varied inaccordance with the predetermined program on successive cycles ofoperation of said machine tool to enable different lengths of bar stockto be pulled from said spindle assembly on successive cycles ofoperation of said machine tool.

7. A machine as set forth in claim 3 wherein said control means furtherincludes numerical control means for storing numerical data which is inaccordance with a predetermined length of bar stock to be pulled fromsaid chuck means by movement of said gripper means away from said oneend portion of said chuck means and means for effecting operation ofsaid actuator means to operate said chuck means to the closed conditionin response to the pulling from said chuck means of the predeterminedlength of bar stock to thereby hold the bar stock against furthermovement relative to said chuck means after the predetermined length ofbar stock has been pulled from said chuck means.

8. A machine as set forth in claim 3 wherein said control means furtherincludes numerical control means for storing numerical data which is inaccordance with the selected length of bar stock to be pulled from saidchuck means by movement of said gripper means relative to said chuckmeans and means for interrupting operation of said means for moving saidgripper means in response to the pulling from said chuck means of alength of bar stock corresponding to the stored numerical data.

9. A machine as set forth in claim 3 wherein said control means includesnumerical control means for controlling operation of said means formoving said gripper means to thereby control the length of bar stockpulled from said chuck means, said numerical control means includingregister means for storing numerical data which is in accordance withthe length of bar stock to be pulled from said chuck means by movementof said gripper means away from said one end portion of said chuck meansand control means for interrupting operation of said means for movingsaid gripper means in response to the pulling from said chuck means of alength of bar stock which is in accordance with the numerical datastored in said register means.

10. A machine as set forth in claim 7 wherein said numerical controlmeans further includes means for operating said machine through aplurality of operating cycles in accordance with a predetermined programand means for enabling the stored numerical data to vary in accordancewith the predetermined program on successive cycles of operation of saidmachine to enable the predetermined length of bar stock pulled from saidchuck means into the work area to be varied on successive cycles ofoperation of said machine.

11. A machine as set forth in claim 2 wherein said actuator means isoperable to operate said chuck means to the closed condition upon thepulling from said chuck means of the length of bar stock which is inaccordance with the numerical data stored in said register means, saidcontrol means being operable to continue of said means for moving saidgripper means away from said one end portion of said chuck means uponoperation of said chuck means to be closed condition to disengage saidgripper means from the bar stock by moving said gripper means relativeto the bar stock.

12. A machine as set forth in claim 2 wherein said numerical controlmeans further includes means for operating said machine through aplurality of operating cycles in accordance with a predetermined programand means for changing the numerical data stored in said register meansin accordance with the predetermined program on successive cycles ofoperation of said machine to enable different lengths of bar stock to bepulled from said chuck means on successive cycles of operation of saidmachine.

1. A machine for operating on bar stock with tools located in a workarea, said maChine comprising chuck means for holding bars stock in aposition in which the bar stock extends away from one end portion ofsaid chuck means into the work area, said chuck means being operablebetween a closed condition holding the bar stock against movementrelative to said chuck means and an open condition in which the barstock is movable relative to said chuck means, actuator means foreffecting operation of said chuck means between the open condition andthe closed condition, gripper means for gripping the bar stock in thework area adjacent to said one end portion of said chuck means, saidgripper means including a plurality or resilient finger elements havingsurfaces defining an opening which is slightly smaller than and has thesame general cross-sectional configuration as the cross-sectionalconfiguration of one end portion of the bar stock, means for moving saidgripper means away from said one end portion of said chuck means to pullbar stock from said chuck means into the work area by moving the portionof bar stock gripped by said gripper means away from said one endportion of said chuck means when said chuck means has been operated tothe open condition by said actuator means, said means for moving saidgripper means being operable to effect gripping engagement of saidgripper means with the bar stock by moving said gripper means towardsaid one end portion of said chuck means when said chuck means is in theclosed condition to press the finger elements against the one endportion of the bar stock and cam the finger elements outwardly toincrease the size of the opening slightly and to move the fingerelements into frictional engagement with an axially extending surface ofthe one end portion of the bar stock while the bar stock is held againstaxial movement by said chuck, means, and control means for controllingthe operation of said actuator means and said means for moving saidgripper means, said control means including means for effectingoperation of said actuator means to operate said chuck means to theclosed condition after bar stock has been pulled from said chuck meansby movement of said gripper means away from said one end portion of saidchuck means and means for disengaging said gripper means from the barstock by continuing the movement of said gripper means away from saidone end portion of said chuck means after said chuck means has beenoperated to the closed condition by said actuator means to slide saidfinger elements out of frictional engagement with the one end portion ofthe bar stock.
 2. A machine for operating on bar stock with toolslocated in a work area, said machine comprising chuck means for holdingbar stock in a position in which the bar stock extends away from one endportion of said chuck means into the work area, said chuck means beingoperable between a closed condition holding the bar stock againstmovement relative to said chuck means and an open condition in which thebar stock is movable relative to said chuck means, actuator means foreffecting operation of said chuck means between the open condition andthe closed condition, gripper means for gripping the bar stock in thework area adjacent to said one end portion of said chuck means, saidgripper means includes a plurality of resilient finger elements havingsurfaces defining an opening which is slightly smaller than and has thesame general cross-sectional configuration as the cross-sectionalconfiguration of one end portion of the bar stock, means for moving saidgripper means away from said one end portion of said chuck means to pullbar stock from said chuck means into the work area by moving the portionof bar stock gripped by said gripper means away from said one endportion of said chuck means when said chuck means has been operated tothe open condition by said actuator means, said means for moving saidgripper means being operable to effect gripping engagement of saidgripper means with the bar stock by moving said gripper means towardsaid one end portion of said Chuck means when said chuck means is in theclosed condition to press the finger elements against the one endportion of the bar stock and cam the finger elements outwardly toincrease the size of the opening slightly and to move the fingerelements into frictional engagement with an axially extending surface ofthe one end portion of the bar stock while the bar stock is held againstaxial movement by said chuck means, and numerical control means forcontrolling operation of said means for moving said gripper means tothereby control the length of bar stock pulled from said chuck means,said numerical control means including register means for storingnumerical data which is in accordance with the length of bar stock to bepulled from said chuck means by movement of said gripper means away fromsaid one end portion of said chuck means and control means forinterrupting operation of said means for moving said gripper means inresponse to the pulling from said chuck means of a length of bar stockwhich is in accordance with the numerical data stored in said registermeans.
 3. A machine for operating on bar stock with tools located in awork area, said machine comprising chuck means for holding bar stock ina position in which the bar stock extends away from one end portion ofsaid chuck means into the work area, said chuck means being operablebetween a closed condition holding the bar stock against movementrelative to said chuck means and an open condition in which the barstock is movable relative to said chuck means, actuator means foreffecting operation of said chuck means between the open condition andthe closed condition, gripper means for gripping the bar stock in thework area adjacent to said one end portion of said chuck means, saidgripper means including surface means for frictionally engaging one endportion of the bar stock, means for moving said gripper means away fromsaid one end portion of said chuck means to pull bar stock from saidchuck means into the work area by moving the portion of bar stockgripped by said gripper means away from said one end portion of saidchuck means when said chuck means has been operated to the opencondition by said actuator means, said means for moving said grippermeans being operable to effect gripping engagement of said gripper meanswith the bar stock by moving said gripper means toward said one endportion of said chuck means when said chuck means is in the closedcondition to press said gripper means against the one end portion of thebar stock and move said surface means into frictional engagement with anaxially extending surface of the one end portion of the bar stock whilethe bar stock is held against axial movement by said chuck means, andcontrol means for controlling the operation of said actuator means andsaid means for moving said gripper means, said control means includingmeans for disengaging said gripper means from the bar stock bycontinuing the movement of said gripper means away from said chuck meansafter said chuck means has been operated to the closed condition by saidactuator means and sliding said surface means along the one end portionof the bar stock to move said surface means out of frictional engagementwith the one end portion of the bar stock.
 4. A machine as set forth inclaim 2 wherein said numerical control means further includes means foroperating said machine through a plurality of operating cycles inaccordance with a predetermined program and means for enabling thestored numerical data to vary in accordance with the predeterminedprogram on successive cycles of operation of said machine to enable thepredetermined length of bar stock pulled from said chuck means into thework area to be varied on successive cycles of operation of saidmachine.
 5. A machine as set forth in claim 1 wherein said control meansincludes numerical control means for controlling operation of said meansfor moving said gripper means to thereby control the length of bar stockpulled from said chuck means, said numerical control means includingregister means for storing numerical data which is in accordance withthe length of bar stock to be pulled from said chuck means by movementof said gripper means away from said one end portion of said chuck meansand control means for interrupting operation of said means for movingsaid gripper means in response to the pulling from said chuck means of alength of bar stock which is in accordance with the numerical datastored in said register means.
 6. A machine as set forth in claim 5wherein said numerical control means further includes means foroperating said machine tool through a plurality of operating cycles inaccordance with a predetermined program and means for enabling thestored numerical data to be varied in accordance with the predeterminedprogram on successive cycles of operation of said machine tool to enabledifferent lengths of bar stock to be pulled from said spindle assemblyon successive cycles of operation of said machine tool.
 7. A machine asset forth in claim 3 wherein said control means further includesnumerical control means for storing numerical data which is inaccordance with a predetermined length of bar stock to be pulled fromsaid chuck means by movement of said gripper means away from said oneend portion of said chuck means and means for effecting operation ofsaid actuator means to operate said chuck means to the closed conditionin response to the pulling from said chuck means of the predeterminedlength of bar stock to thereby hold the bar stock against furthermovement relative to said chuck means after the predetermined length ofbar stock has been pulled from said chuck means.
 8. A machine as setforth in claim 3 wherein said control means further includes numericalcontrol means for storing numerical data which is in accordance with theselected length of bar stock to be pulled from said chuck means bymovement of said gripper means relative to said chuck means and meansfor interrupting operation of said means for moving said gripper meansin response to the pulling from said chuck means of a length of barstock corresponding to the stored numerical data.
 9. A machine as setforth in claim 3 wherein said control means includes numerical controlmeans for controlling operation of said means for moving said grippermeans to thereby control the length of bar stock pulled from said chuckmeans, said numerical control means including register means for storingnumerical data which is in accordance with the length of bar stock to bepulled from said chuck means by movement of said gripper means away fromsaid one end portion of said chuck means and control means forinterrupting operation of said means for moving said gripper means inresponse to the pulling from said chuck means of a length of bar stockwhich is in accordance with the numerical data stored in said registermeans.
 10. A machine as set forth in claim 7 wherein said numericalcontrol means further includes means for operating said machine througha plurality of operating cycles in accordance with a predeterminedprogram and means for enabling the stored numerical data to vary inaccordance with the predetermined program on successive cycles ofoperation of said machine to enable the predetermined length of barstock pulled from said chuck means into the work area to be varied onsuccessive cycles of operation of said machine.
 11. A machine as setforth in claim 2 wherein said actuator means is operable to operate saidchuck means to the closed condition upon the pulling from said chuckmeans of the length of bar stock which is in accordance with thenumerical data stored in said register means, said control means beingoperable to continue of said means for moving said gripper means awayfrom said one end portion of said chuck means upon operation of saidchuck means to be closed condition to disengage said gripper means fromthe bar stock by moving said gripper means relative to the bar stock.12. A machine as set fOrth in claim 2 wherein said numerical controlmeans further includes means for operating said machine through aplurality of operating cycles in accordance with a predetermined programand means for changing the numerical data stored in said register meansin accordance with the predetermined program on successive cycles ofoperation of said machine to enable different lengths of bar stock to bepulled from said chuck means on successive cycles of operation of saidmachine.